Here's how: After it detects a Streptococcus infection, the body's immune system responds by creating lots of antibodies. While these antibodies do fight the Streptococcus bacteria (a good thing), they also sometimes mistakenly attack the heart, joints, and brain (a very, very bad thing.)

In children, this attack on the brain can cause the bundle of nerves called the basal ganglia to become inflamed. This, in turn, can cause kids to develop, seemingly overnight, severe symptoms of OCD and anorexia.

As a press release today put it:

"Parents will describe children with [Pediatric Acute-onset Neuropsychiatric Syndrome (PANS)] as overcome by a 'ferocious' onset of obsessive thoughts, compulsive rituals and overwhelming fears."

Here are some heartbreaking examples of the kinds of behaviors children stricken with PANS may display, practically out of nowhere (taken from the NIMS website):

appearing terror stricken

suffering extreme separation anxiety

shifting from laughter to tears for no apparent reason

regressing to temper tantrums, "baby talk," or bedwetting

undergoing sudden deterioration in school performance or learning abilities

exhibiting sensory and motor abnormalities

So, if you encounter a kid doing any of the above, they are either just being a kid or they are afflicted with an extremely debilitating neuropsychiatric syndrome.

The NIMH has now launched a clinical trial to test the effectiveness of antibody treatments on reversing the symptoms of children diagnosed with PANS. The study will also attempt to determine whether there is a culprit other than strep bacteria (still a somewhat controversial theory) at the root of the problem.